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COPD for ABIM

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Chronic obstructive pulmonary disease for the American Board of Internal Medicine Exam
Pathophysiology
  • Chronic Inflammation:
    • Chronic obstructive pulmonary disease (COPD) involves persistent inflammation of the airways, lung parenchyma, and vasculature.
    • Inhaled irritants (e.g., cigarette smoke, pollutants) cause damage to airway structures, leading to an exaggerated inflammatory response.
    • Neutrophils, macrophages, and CD8+ T cells are the predominant cells involved in COPD-related inflammation.
  • Airflow Limitation:
    • COPD is characterized by progressive airflow obstruction due to:
    • Small airway disease (bronchiolitis): Narrowing and obliteration of the small airways caused by inflammation, fibrosis, and increased mucus production.
small airway disease
    • Parenchymal destruction: Emphysema leads to the loss of elastic recoil, resulting in reduced ability to keep airways open during expiration.
  • Imbalance of Protease-Antiprotease Activity:
    • In COPD, there is an increase in protease activity (e.g., neutrophil elastase) and a decrease in antiprotease activity (e.g., alpha-1 antitrypsin).
    • This imbalance contributes to alveolar destruction and emphysema development.
  • Oxidative Stress:
    • Oxidants from cigarette smoke and the inflammatory cells in COPD contribute to further lung damage, inactivation of antiproteases, and inflammation amplification.
Risk Factors
  • Cigarette Smoking:
    • The primary risk factor for COPD, responsible for 85-90% of cases.
    • The risk increases with pack-years of smoking, but even light smokers can develop COPD.
  • Environmental/Occupational Exposure:
    • Chronic exposure to biomass fuels, air pollution, and occupational dusts and chemicals increases the risk of developing COPD.
  • Genetics:
    • Alpha-1 antitrypsin deficiency is a genetic risk factor for COPD, especially for early-onset emphysema.
  • Aging:
    • The lungs undergo structural changes with age, and older adults are more susceptible to COPD.
Clinical Features
  • Chronic Cough and Sputum Production:
    • Often the earliest symptom, cough may be intermittent or persistent. It is usually accompanied by mucous sputum production.
  • Dyspnea:
    • Progressive shortness of breath, especially during exertion, is a hallmark symptom. It is typically the reason patients seek medical care.
  • Wheezing and Chest Tightness:
    • These symptoms are common, especially during exacerbations, and are often mistaken for asthma.
  • Frequent Respiratory Infections:
    • Patients with COPD are more susceptible to respiratory infections, which can lead to exacerbations.
Diagnosis
  • Spirometry:
    • Spirometry is essential for diagnosing COPD and assessing its severity. Key parameters include:
    • Forced Expiratory Volume in 1 Second (FEV1): Decreased in COPD.
    • Forced Vital Capacity (FVC): May also be reduced, but to a lesser extent than FEV1.
    • FEV1/FVC Ratio: A post-bronchodilator ratio <0.70 confirms persistent airflow limitation and the diagnosis of COPD.
  • Assessment of Severity:
    • The severity of COPD is classified based on FEV1:
    • Mild (GOLD 1): FEV1 ≥80% predicted.
    • Moderate (GOLD 2): FEV1 50-79% predicted.
    • Severe (GOLD 3): FEV1 30-49% predicted.
    • Very Severe (GOLD 4): FEV1 <30% predicted.
Management
  • Smoking Cessation:
    • The most critical intervention to slow disease progression. Pharmacologic aids (nicotine replacement, varenicline, bupropion) and counseling significantly improve quit rates.
  • Bronchodilators:
    • Mainstay of COPD therapy, used to relieve symptoms and reduce exacerbations.
    • Short-acting bronchodilators (SABAs): e.g., albuterol, used as needed for relief of symptoms.
    • Long-acting bronchodilators (LABAs and LAMAs): e.g., salmeterol (LABA), tiotropium (LAMA), used for maintenance therapy in moderate-to-severe COPD.
    • Combination bronchodilators: LABA/LAMA combinations are superior to monotherapy in improving lung function and reducing exacerbations.
  • Inhaled Corticosteroids (ICS):
    • Used in combination with bronchodilators (LABA/ICS) in patients with severe COPD or frequent exacerbations.
    • ICS are associated with a reduced risk of exacerbations but carry an increased risk of pneumonia.
  • Phosphodiesterase-4 (PDE-4) Inhibitors:
    • Roflumilast can be added in severe COPD with chronic bronchitis and frequent exacerbations, as it reduces inflammation and exacerbation frequency.
  • Oxygen Therapy:
    • Long-term oxygen therapy improves survival in patients with chronic respiratory failure and severe resting hypoxemia (PaO2 ≤55 mmHg or SpO2 ≤88%).
  • Pulmonary Rehabilitation:
    • Improves exercise tolerance, dyspnea, and quality of life in all patients with COPD, especially those with moderate-to-severe disease.
  • Vaccinations:
    • Annual influenza vaccination and pneumococcal vaccination (PPSV23, PCV13) are recommended to reduce the risk of respiratory infections and exacerbations.
Exacerbations
  • Definition:
    • Acute worsening of respiratory symptoms (dyspnea, cough, sputum production) beyond normal day-to-day variations, requiring a change in treatment.
  • Causes:
    • Most exacerbations are triggered by respiratory infections (viral or bacterial). Environmental pollutants may also contribute.
  • Management of Exacerbations:
    • Bronchodilators: SABAs (with or without short-acting anticholinergics) are first-line treatments for exacerbations.
    • Corticosteroids: Oral prednisone (40 mg daily for 5 days) is commonly used to shorten recovery time and improve lung function.
    • Antibiotics: Indicated if increased sputum purulence is present, or if mechanical ventilation is required.
    • Oxygen Therapy: Target SpO2 is 88-92% to prevent hypoxia while avoiding hypercapnia in patients with severe COPD.
Complications
  • Cor Pulmonale:
    • COPD can lead to pulmonary hypertension and right heart failure (cor pulmonale), characterized by peripheral edema, jugular venous distension, and hepatomegaly.
  • Acute Respiratory Failure:
    • Severe exacerbations can lead to acute respiratory failure, requiring mechanical ventilation or non-invasive positive pressure ventilation (NIPPV).
Key Points
  • COPD is characterized by persistent airflow limitation due to chronic inflammation, airway obstruction, and parenchymal destruction.
  • Cigarette smoking is the leading risk factor for COPD, though environmental exposures and genetics (e.g., alpha-1 antitrypsin deficiency) also play a role.
  • Diagnosis is confirmed by spirometry, showing a post-bronchodilator FEV1/FVC ratio <0.70.
  • Management includes smoking cessation, bronchodilators, inhaled corticosteroids, pulmonary rehabilitation, and vaccinations.
  • Exacerbations are treated with bronchodilators, corticosteroids, and antibiotics when indicated. Oxygen therapy is used to manage hypoxemia.
  • Complications include cor pulmonale and acute respiratory failure, which may necessitate advanced interventions.

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